RK: Adam Nash, the former chief executive of digital financial advice company Wealthfront, has joined the board of U.S. micro-investing app Acorns, the company said on Tuesday.

Nash, who stepped down from his role at Wealthfront in December, will advise the investment startup as it expands its breadth of products aimed at helping younger investors save.

The company also said it had appointed Shlomo Benartzi, professor and co-chair of the Behavioral Decision-Making Group at the University of California, Los Angeles, to its board. Benartzi will help the company understand what drives saving so that it can design better products.

"We are working with a team of behavioral economists across the country to help nudge our customers along in their financial journey," said Noah Kerner, Acorns CEO.

Based in Newport Beach, California, Acorns rounds up purchases from clients' card transactions to the nearest dollar and automatically invests the change into portfolios of low-cost exchange-traded funds.

Launched in 2014, the startup currently counts more than 1.6 million investment accounts, it said. Investor include payments company PayPal Inc and Japanese e-commerce company Rakuten.

Acorns is one of a growing group of young fintech companies that use automation to make investing easier and cheaper for a segment of clients previously seen as too expensive to serve.

Wealthfront was one of the earliest and best-known companies in the so-called robo-advice sector, alongside competitor Betterment LLC. While startups pioneered the robo-advice model, they have recently faced more competition from established players, raising questions about their prospects.

Reuters reported last month that Goldman Sachs was planning to launch a robo-adviser geared to mass affluent clients.

Nash, who had joined Wealthfront in 2013, was previously vice president of product management at professional networking site LinkedIn Corp and held senior roles at eBay Inc.